Nope, being illegal means something else. Nobody is going to be fined or go to jail for openly boycotting Israel. An amusement park can boycott Israel, they can say so in big bold letters on their commercials etc, and the state isn’t going to do anything.

Therefore All companies ARE allowed to “boycott energy companies, discriminate against firearm entities or associations, or boycott Israel” https://texasattorneygeneral.gov/sites/default/files/images/...

Not doing business is something else. States regularly prohibit companies over 500 employees from signing specific contracts, that doesn’t make it illegal to be a company with over 500 employees.